US peanuts are planted after the last frost in April or May when soil temperatures reach 65‐70°F (20°C). Pre‐planting tillage ensures a well‐prepared seedbed.
Certified peanut seeds are planted 4‐5cm deep, one every 5‐10cm in the SE and SW, and 10‐15cm in the V‐C area. The row spacing is determined to a large extent by the type of planting and harvesting equipment used.
Peanut seedlings crack the soil about 10 days after planting and grow into green oval‐leafed plants about 45cm tall.
A climate with 200 frost‐free days is required for a good crop. Farmers may utilize irrigation in an effort to reduce crop stress and produce the highest quality peanuts.
Peanuts flower about 30 days after planting and continue to produce flowers over a 90‐120 day period, resulting in peanuts maturing at different rates on the plant.
Once the flowers pollinate themselves, the petals fall off as the peanut ovary begins to form.This budding ovary, called a ‘peg’, grows away from the plant on a vine and penetrates the soil to become a peanut.
As the plant produces ovaries at different times, the peanuts growing beneath the ground mature at different rates, as can be seen here.
The peanut is a nitrogen‐ fixing plant. Its roots form nodules that absorb nitrogen from the air and provide enrichment and nutrition to the plant and soil.
Integrated pest management is utilized in order to control weeds, diseases and insects.
From planting to harvesting, the growing cycle takes about 4‐5 months, depending on the type or variety.
The peanut harvesting process occurs in two stages. Digging, which is the first, begins when about 70% of the pods have reached maturity. Harvesting peanuts at the peak of their maturity is necessary to reap the fullest peanut flavor possible.
A digger proceeds along the rows of plants, driving a horizontal blade 10‐15cm under the soil, loosens the soil and cuts the tap root.
Behind the blade, a shaker lifts the plant from the soil, gently shakes the earth from the peanuts, rotates the plant and lays the plant back down in ‘windrow’, peanuts up and leaves down. When dug, peanuts contain 25‐50% moisture which must be reduced for safe storage.
The inverted peanuts are left to dry in the field for 2 or more days until they reach the appropriate moisture content.
The peanuts are now ready for the second phase of harvesting— threshing, or combining.
A combine sweeps over the windrows. The combine lifts the plants, separates the peanuts from the vine, blows them into a hopper on top of the machine and lays the vine back down in the field. The vines are returned to the field to improve soil fertility and organic matter.
Freshly harvested peanut pods are transferred to drying wagons and taken to buying points for further drying. Forced hot air is slowly circulated through the drying wagons. In the curing process, moisture content is reduced to 8‐ 10% for safe storage.
After curing, the peanuts are inspected and graded to establish quality and value of the product. This is done by the Agricultural Marketing Service of the US Department of Agriculture at buying stations or shelling plants.
After grading, the peanuts are moved to bulk warehouses for storage prior to shelling. New technologies such as dome‐shaped warehouses are helping to maintain the quality of the peanuts.
After grading, peanuts are either cleaned for sale as inshell peanuts, or shelled for further processing. During the shelling process the peanuts are cleaned (soil, vines etc are removed) and then de‐hulled using perforated grates before being sorted into market grades. High‐speed electronic colour sorting machines eliminate discoloured or defective kernels.
US peanuts are the only commodity to be accepted by the EU for pre‐export testing certification at origin. Rigorous aflatoxin testing is conducted in the US prior to shipment of goods to ensure that products meet the EU specifications, resulting in far fewer tests on import into the EU and thus ensuring quicker transit times to manufacturers.
The US peanut industry continues to invest in innovative ways to control humidity and storage temperature, and has dedicated cold storage facilities to help maintain the best tasting peanuts for our customers.
The US is able to offer a range of peanut ingredients for applications including bakery, confectionery, ice cream and the general consumer market. These include peanut flour, oil, extract and peanut butter as well as custom processed peanuts.